I too wondered how their image quality might be expected to vary with time. I used images from Hubble, Herschel, and Planck, if I recall correctly. I believe that they included visible, infrared, ultraviolet, and radio wavelengths.Concerning comments in post #23, perhaps space.com can publish an *official* article here on the topic. Dust clouds in space face a very harsh environment like photoevaporation and dissipation, example activity in M42 in Orion or other areas observed in the interstellar medium. What would be the expected lifetime for *space art* to survive where earthlings would see and understand the message?, What is the min distance from earth? What is the max image distance?, etc. Specific sky positions are needed (celestial coordinate system) and follow up observations using different equipment and perhaps different wavelengths of light too. How long have these space art images been documented?
Some areas, where much star formation occurs, experience dust motion and pillar formation due to light pressure from new stars. And some areas were said to have what amount to very high velocity winds (from what, exactly, I forget). Some areas where face artworks were seen were in still-expanding supernova remnants, such as the Crab Nebula. I am sure that there are many other time-varying phenomena involved.
A few of the nebula images I studied were from less than 1000 light years from earth. Many are from 5000 to 25,000 light years away. There are also quite a few that are from about 170,000 light years away (in the Magellanic Clouds). Some are from Planck whole-sky images and could be over a very wide range of distances. But one chapter's images are all from the core of the galaxy M42, which is 12 million light years from here. Other recognizable face artworks have been seen at much greater distances.